Shroud and cyclonic cleaning apparatus incorporating same

ABSTRACT

The invention provides a shroud (10; 40) for use in apparatus incorporating cyclonic dust separation structure for separating dirt and dust from an airflow, the shroud (10; 40) including a perforated portion (14; 44) having a multiplicity of perforations (30; 46) for allowing the airflow to pass therethrough. According to invention, the perforated portion (14) has a lower edge (16) and a lip (18) depending therefrom, the lip (18) including a parallel-sided portion (34) having an inclined distal end and a step (38) formed radially inwardly of the parallel-sided portion (34) and at the proximal end thereof. The invention improves performance of the dust separation apparatus in conjunction with which the shroud (10; 40) is utilized.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not Applicable

CROSS-REFERENCES TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to an improved shroud and to apparatusincorporating an improved shroud.

A shroud is used in conjunction with cyclonic dust separation means tofilter an airflow. In apparatus incorporating dual cyclonic separationmeans, ie. two separate cyclones arranged in series to remove,initially, larger pieces of dirt and fluff and, subsequently, finer dustparticles, the shroud is positioned between the two cyclone arrangementsand the airflow is passed through the shroud to reduce the possibilityof larger pieces of dust and fluff entering the second, high efficiencycyclone.

(2) Description of the Related Art

It has been found that various features of the shroud have an effect onthe overall performance of the separation means. It is therefore anobject of the invention to provide a shroud which improves the overallperformance of the cyclonic dust separation means in conjunction withwhich it is used.

PRESENT SUMMARY OF THE INVENTION

The invention provides a shroud as claimed in claim

Advantageous and preferable features are set out in the detaileddescription. When used in conjunction with dual cyclonic separationmeans, these arrangements improve the percentage of dirt, dust and fluffremaining in the low efficiency cyclone which, in turn, improves theperformance of the high efficiency cyclone and thus of the entireseparation means.

Embodiments of the invention will now be described with reference to theaccompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view, partially in section, of a shroud incorporatingthe present invention;

FIG. 2a is an enlarged sectional view of part of the wall of theperforated portion of the embodiment shown in FIG. 1;

FIG. 2b is an enlarged detail of the embodiment shown in FIG. 1;

FIG. 3 is a side view of a second embodiment of the present invention;and

FIG. 3a is an enlarged section through part of the wall of theperforated section of the embodiment shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a shroud 10 having a cylindrical portion 12 in which islocated a perforated portion 14. The perforated portion 14 has a loweredge 16 from which depends a lip 18 which will be described in greaterdetail below. Extending radially inwardly from the lower edge 16 of theperforated portion 14 is an annular web 20 which communicates with orseals against an inner cyclone 22. The inner cyclone 22 forms no part ofthe present invention and will not be described in any further detailhere. The web 20 effectively forms support means for and a seal againstthe cylindrical portion 12. Further support and sealing means 24 arelocated at the upper edge of the cylindrical portion 12 but which,again, do not form part of the present invention, except to support thecylindrical portion 12.

FIG. 2a shows, in sectional view, a portion of the wall 26 forming theperforated portion 14. The wall 26 has an upstream surface 28 and amultiplicity of perforations 30 through which, in use, the airflowpasses in the direction of arrows 32. In prior art shrouds, theperforations have been formed in such a manner that the upstream edge ofeach perforation incorporates a radius at its intersection with theupstream surface of the shroud. According to the present invention, theupstream edge of each perforation 30 meets the upstream surface 28 at asharply defined angle. Such an angle can be produced by forming theperforations 30 by drilling or, if desired, by molding or any othersuitable manufacturing process. The provision of a sharp angle at theintersection between the upstream edge of each perforation 30 and theupstream surface 28 of the shroud 10 decreases the amount of fine dustpassing through the perforations 30 and therefore decreases the risk ofthe perforations 30 becoming blocked by dust and fluff particles.

The thickness of the material t forming the wall 26 is substantially 2mm. The diameter d of each cylindrical perforation 30 is substantially2.2 mm.

The embodiment shown in FIG. 1 includes a lip 18 depending from thelower edge 16 of the perforated portion 14. The lip 18, which is shownin more detail in FIG. 2b, essentially comprises a parallel sidedportion 34 extending substantially parallel to the longitudinal axis 36of the shroud 10. The distal end of the parallel-sided portion 34 isinclined at an angle α of substantially 45°. At the proximal end of thelip 18, a step 38 is formed, the breadth b of the step 38 beingsubstantially the same as the breadth B of the parallel-sided portion34. Both the breadth b and the breadth B are, in the embodiment shown,substantially 2 mm.

The height h of the step 38 corresponds substantially to the breadth bof the step 38 and, again, is approximately 2 mm in this embodiment.

The distance x to which the lip 18 extends below the lower edge 16 ofthe perforated portion 14 is approximately 15 mm.

It has been found that this shape of bottom lip 18 of the shroud 10reduces the amount of blockage of the perforations 30 in the shroud 10and the amount of fine dust passing through the perforations 30 whenused in dual cyclonic vacuum cleaning apparatus with the shroud 10 beingpositioned in the airflow path between a low efficiency cyclone and ahigh efficiency cyclone. A relatively large proportion of dirt and dustis retained in the low efficiency cyclone and the step 38 also improvesthe seal between the lip 18 and the lower edge 16 of the perforatedsection 14.

FIG. 3 illustrates a second embodiment of the invention. In FIG. 3, afrusto-conical shroud 40 is illustrated having support means 42 locatedat the upper end thereof. A frusto-conical perforated portion 44 islocated in the frusto-conical shroud 40. A multiplicity of perforations46 are arranged in the perforated portion 44 and FIG. 3a is a sectionalview through part of the side wall 48 of the perforated portion 44.

As can be seen from FIG. 3a, the thickness t of the material forming theside wall 48 of the shroud 40 is substantially 2 mm. Also, the diameterd of each cylindrical perforation 46 is substantially 2.2 mm. Thelongitudinal axis of each perforation 46 is substantially perpendicularto the longitudinal axis 50 of the shroud 40 and the angle at which theinterior wall of each perforation meets the external surface of the sidewall 48 is sharply defined.

In the embodiment shown, the angle of inclination β of the side wall 48to the longitudinal axis 50 of the shroud 40 is substantially 12.5°.However, this angle could be varied according to the requirements of thecyclonic dust separating apparatus and particularly to the angle ofinclination of the inclined wall of the high efficiency cyclone. Theangle of inclination β is preferably substantially identical to theangle of inclination of the wall of the high efficiency cyclone so thatthe wall 48 of the shroud 40 can be located parallel to the inclinedwall of the high efficiency cyclone whilst still providing for thepassage of air between the perforations and the high efficiency cyclone.

It has been found that the provision of sharply defined perforations 46having a diameter of 2.2 mm is advantageous in that the amount of finedust passing through the shroud is reduced thus reducing the likelihoodof the shroud becoming blocked by dust or fluff. The provision of aconical shroud 40 increases the volume of the area of the low efficienctcyclone in which dirt and dust is collected thus increasing the capacityof the cyclone.

It will be appreciated by a skilled reader that the invention is notlimited to the embodiments illustrated above. Various modifications andalterations will be apparent to the skilled reader as falling within thescope of the invention.

I claim:
 1. A shroud for use in apparatus incorporating cyclonic dustseparation means for separating dirt and dust from an airflow, theshroud comprising a perforated portion having a lower edge and a lipdepending therefrom, the lip comprising a parallel-sided portion havingan inclined distal end, wherein a step is formed radially inwardly ofthe parallel-sided portion and at the proximal end thereof.
 2. A shroudas claimed in claim 1, wherein the breadth of the step is substantiallyequal to the breadth of the parallel-sided portion.
 3. A shroud asclaimed in claim 1 or 2, wherein the height of the step is substantiallyequal to the breadth thereof.
 4. A shroud as claimed in any one ofclaims 1 or 2 wherein the breadth of the parallel-sided portion issubstantially 2 mm.
 5. A shroud as claimed in any one of claims 1 or 2wherein the parallel-sided portion extends substantially parallel to thelongitudinal axis of the shroud.
 6. A shroud as claimed in any one ofclaims 1 or 2 wherein the lip extends substantially 15 mm below thelower edge of the perforated portion.
 7. A shroud as claimed in any oneof claims 1 or 2 wherein the distal end of the lip is inclined at anangle of substantially 45° to the parallel sides of the lip.
 8. A shroudas claimed in any one of claims 1 or 2 wherein the perforated portion iscylindrical.
 9. Apparatus as claimed in claim 1 wherein the cyclonicdust separation means comprise a low efficiency cyclone and a highefficiency cyclone positioned downstream of the low efficiency cyclone,the shroud being positioned between the two cyclones.
 10. Apparatus asclaimed in claim 9 wherein the apparatus consists of a vacuum cleaner.11. A shroud as claimed in claim 3 wherein the parallel-sided portionextends substantially parallel to the longitudinal axis of the shroud.12. A shroud as claimed in claim 4 wherein the parallel-sided portionextends substantially parallel to the longitudinal axis of the shroud.13. A shroud as claimed in claim 3 wherein the perforated portion iscylindrical.
 14. A shroud as claimed in claim 4 wherein the perforatedportion is cylindrical.
 15. A shroud as claimed in claim 5 wherein theperforated portion is cylindrical.
 16. A shroud as claimed in claim 6wherein the perforated portion is cylindrical.
 17. A shroud as claimedin claim 7 wherein the perforated portion is cylindrical.
 18. A shroudas claimed in claim 11 wherein the perforated portion is cylindrical.19. A shroud as claimed in claim 12 wherein the perforated portion iscylindrical.